Autonomous vehicles (AVs) exploring in an unknown environment are made to face many challenges while navigating in a planned or unplanned trajectory to reach their destination. Many AV tasks rely on accurate knowledge of their position and orientation in space. Localization is the process of determining an AV's position accurately on the surface of the earth. AVs compute estimates of their poses (i.e. the combination of position and orientation) based on available absolute and relative measurements. Absolute measurements generally rely on the availability of radio-navigation-satellite services (RNSS) systems such as Global Positioning System (GPS), GLONASS, Galileo, and BeiDou.
When RNSS data is not available due to environmental or structural interference, such as in outdoor parking lots, indoor parking structures, tunnels, and canyons, other technologies may be used to obtain relative measurements. For example, these technologies may include ultrasonic positioning systems, ultra-wideband systems, dedicated short-range communications systems (DSRC), cellular systems, AM/FM radio, satellite communications, digital television, Wi-Fi, light detection and ranging (LiDAR), radar, video imaging, or combinations thereof. Cellular, AM/FM radio, satellite communications, digital television, and Wi-Fi. Cellular, AM/FM radio, satellite communication, digital television (HDTV), Wi-Fi are known as signals of opportunity (SOP), ambient signals not intended for positioning, navigation, and timing. AVs are assumed to be equipped, at a minimum, with RNSS and SOP receivers, microelectromechanical systems (MEMS) inertial measurement unit (IMUs), wheel speed sensors/wheel encoders/vehicle speed sensors (VSS) (collectively wheel sensors), processing hardware and software. AVs may also have cameras so that SOPs may further include available active sources of light such as street light, parking lot lights or structure/building lights.
Traditional approaches to address RNSS limitations have been to fuse RNSS receivers with dead-reckoning systems and map-matching algorithms. However, localization determined from multiple homogeneous or heterogeneous sensors may suffer from loss of high positioning accuracy, single point failure, and energy inefficiency, and communication delay and packet loss depending on the localization techniques employed.